The pituitary uptake of In-111-DTPA-D-Phe(1)-octreotide in the normal pituitary and in pituitary adenomas

The aim of this study was to compare the pituitary In-111-DTPA-D-Phe(1)-oct reotide uptake measured in 49 patients subjected to the scintigraphy for SS -R expressing tumors not located in the sellar region with that measured in 38 patients with pituitary adenomas. The 87 subjects enrolled in this stud y were divided into two groups: the first included SSR-expressing tumors (S S-ET), 10 thymomas, 13 differentiated thyroid carcinomas, 4 carcinoids, 5 n euroendocrine tumors, 5 insulinomas, 6 melanomas, 2 renal carcinomas, 2 phe ocromocytomas, and 2 parathyroid tumors, while the second included pituitar y adenomas, 25 GH-secreting, 4 GH/PRL-mixed and 9 clinically nonfunctioning adenomas (NFA). Planar and single-photon-emission tomography images of the head were obtained 2-4 and 24 hours after the injection of 77-103 MBq of I n-111-DTPA-D-Phe(1)-octreotide and pituitary uptake was measured by the reg ion of interest method. A 4 point score was used to grade the pituitary-to- blood (T-to-B) ratios: 0=negative; 1=faint (T-to-B=<1.5); 2=moderate (T-to- B=1.6-3.5); 3=intense (T-to-B=>3.5). In patients with pituitary adenomas, t he percent suppression of GH and alpha-subunit levels after 6-12 months of octreotide treatment (0.3-0.6 mg/day) was correlated to T-to-B ratios. Afte r 2-4 hr from injection, pituitary In-111-DTPA-D-Phe(1)-octreotide uptake w as moderate/intense in 2 out of 49 SS-ET (4%), 18 out of 29 acromegalics (6 2%) and 6 NFA (66.6%), while a faint uptake was detected in 4 SS-ET (8%), 8 GH-secreting adenomas (27.5%) and 3 NFA (33.3%). Negative scan was detecte d in the remaining 43 SS-ET (87.7%) and 3 GH-secreting microadenomas (10.3% ). 24 hr after injection, pituitary In-111-DTPA-D-Phe(1)-octreotide uptake was moderate/intense in SS-ET (10.2%), 21 GH-secreting adenomas (72.4%), an d 9 NFA (100%) while a faint uptake was detectable in 15 SS-ET (30.6%), and 6 GH-secreting adenomas (20.7%). No uptake was visualized in 29 SS-ET, and 2 GH-secreting adenomas. By MRI a pituitary tumor was shown in the 2 SS-ET with early moderate tracer uptake. Normalization of circulating GH/IGF-I l evels and suppression of alpha-subunit levels was achieved in 16 of 18 acro megalics (88.9%) and 5 of 6 NEA-bearing patients, respectively, with scan s cored 2-3 at early images. Eleven acromegalics (37.9%) and 2 NFA (22.2%) di splayed significant tumor shrinkage (greater than or equal to 30% of baseli ne size) during long-term octreotide therapy. Both in GH-secreting and in N EA, a significant correlation was found between percent GH or alpha-subunit suppression after 6-12 months of octreotide therapy and T-to-B ratios both in early (r=0.626; p<0.0001 and r=0.738, p=0.003, respectively) and late i mages (r=0.569; p=0.002 and r=0.8, p=0.01, respectively). In conclusion, th e In-111-DTPA-D-Phe(1)-octreotide uptake in pituitary adenomas was signific antly correlated to octreotide treatment. However, since pituitary In-111-D TPA-D-Phe(1)-octreotide uptake was clearly detectable in 40% of patients wi th SS-ET not located in the pituitary region at 24 hr post-injection, In-11 1-DTPA-D-Phe(1)-octreotide scintigraphy with late pituitary images can not be considered an useful method to predict the chronic responsiveness to oct reotide in individual patients. Caution should also be taken in evaluating the results of the scintigraphy with early images in patients with scant up take before excluding them from treatment. (C) 1999, Editrice Kurtis.